Three-dimensional image display device, three-dimensional image display method, and computer program product for three-dimensional image display

ABSTRACT

A three-dimensional image display device includes a two-dimensional image display screen having color filters in which each color is disposed on sub-pixels obtained by dividing one pixel in a vertical direction and same color is disposed on each column of sub-pixels; an optical plate having an exit pupil, the exit pupil being provided for making a viewing zone different for each pixel and having a longitudinal axis disposed as to be inclined from a vertical direction of the two-dimensional image display screen at a degree (θ) (θ≠0, −45°&lt;θ&lt;45°), the viewing zone being a region in which parallax information displayed on the two-dimensional image display screen is observed; and a viewing zone adjusting unit that adjusts the viewing zone by shifting the viewing zone in a horizontal direction of the two-dimensional image display screen by shifting the parallax information disposed on each pixel of the two-dimensional image display screen in the vertical direction by pixel.

TECHNICAL FIELD

The present invention relates to a three-dimensional image displaydevice, a method of displaying a three-dimensional image, and a computerprogram product for displaying a three-dimensional image, according towhich a parallax information is displayed.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2005-283478, filed on Sep. 29,2005; the entire contents of which are incorporated herein by reference.

BACKGROUND ART

A naked-eye type three-dimensional image display device, in which theparallax information is spatially cut in a horizontal direction andpresented, has been known. An observer can recognize a three-dimensionalimage by observing the parallax information according to his/herposition, further, to a position of his/her eyes.

Many of the three-dimensional image display devices are specificallystructured by a combination of a flat panel display (FPD) such as aliquid crystal display (LCD) and a plasma display panel (PDP), and anoptical plate represented by a lens array and a pinhole array, or thelike.

In the case of the lens, a ray emitted from a point in a pixel of theFPD exits as a substantially parallel light, when the FPD is positionedsubstantially at a focal distance of the lens. Since a pixel has alimited size, the ray emitted from the pixel is incident on a certainrange. In the case of the pinhole, the ray emitted from a pixel goesthrough the pinhole, whereby a direction, to which the ray exits, islimited. By making the direction to which the ray exits and thedirection in which image information to be displayed on the pixel fromwhich the ray is emitted is obtained substantially conform to eachother, an appropriate image can be seen according to the position of theobserver, further to the position of the eyes of the observer. Then, theimage is recognized as the three-dimensional image. The lens and thepinhole are called as an exit pupil.

In the structure of such naked-eye type three-dimensional image displaydevice, it is required to relate a plurality of pixels for displayingtwo-dimensional image for displaying the parallax information, that is,an elemental image, to one pixel for displaying three-dimensional image(lens and pinhole).

Since the number of pixels of the FPD is limited, there is a trade-offrelation, that is, if the parallax information is increased, definitionof the three-dimensional image is deteriorated, whereas if thedefinition of the three-dimensional image is improved, parallax numberis decreased. In order to restrain the deterioration of the definitionof the three-dimensional image and of the parallax number, a method topresent the parallax information only in the horizontal direction, hasbeen known. The three-dimensional image display device thus presentingthe parallax information only in the horizontal direction is called as ahorizontal parallax type three-dimensional image display device.

On the other hand, when only a limited number of pixels for displayingthe two-dimensional image are assigned to one pixel (lens and pinhole)for displaying the three-dimensional image, parallax information can bepresented only in a limited range, in other words, a range in which thethree-dimensional image can be observed is limited. In order to solvesuch a problem, there has been a method of performing tracking of theposition of the observer, thereby shifting a group of pixels fordisplaying the two-dimensional image assigned to the pixel fordisplaying three-dimensional image, namely, a method of shifting adisplay position of the elemental image (for example, refer to JapanesePatent Application Laid-Open No. H09-233500).

DISCLOSURE OF INVENTION

However, the horizontal parallax type three-dimensional image displaydevice is easily affected by position change of the observer, when theexit pupil is inclined from the vertical direction of the displayscreen. Specifically, if the observer moves, the viewing zone in whichthe three-dimensional image is observed is shifted in the horizontaldirection of the display screen. This problem is especially obvious whenthe horizontal parallax type three-dimensional image display device isset such that a display surface thereof is horizontal, that is, in theso-called flatbed display. In the flatbed display, y coordinate isaffected by the position and sitting height of the observer, and is easyto change as compared to that in a vertically-set device.

Further, a positioning of the two-dimensional image display device andthe optical plate is required to have a sufficient accuracy, for thepositioning relates to a visual region of the three-dimensional imagedisplay device. In the horizontal parallax type devices, the parallaxinformation is sometimes disposed by sub-pixel pitch of the FPD in orderto increase the horizontal parallax number. In this case, the parallaxinformation is shifted by one with shift by sub-pixel width(approximately 50 μm). When the exit pupil is inclined from the verticaldirection, an angle of depression, that is, y-coordinate is required tobe tentatively defined for the setting of the visual region. Hence, thepositioning becomes more difficult.

According to one aspect of the present invention, a three-dimensionalimage display device includes a two-dimensional image display screenhaving color filters in which each color is disposed on sub-pixelsobtained by dividing one pixel in a vertical direction and same color isdisposed on each column of sub-pixels; an optical plate having an exitpupil, the exit pupil being provided for making a viewing zone differentfor each pixel and having a longitudinal axis disposed as to be inclinedfrom a vertical direction of the two-dimensional image display screen ata degree (θ) (θ≠0, −45°<θ<45°), the viewing zone being a region in whichparallax information displayed on the two-dimensional image displayscreen is observed; and a viewing zone adjusting unit that adjusts theviewing zone by shifting the viewing zone in a horizontal direction ofthe two-dimensional image display screen by shifting the parallaxinformation disposed on each pixel of the two-dimensional image displayscreen in the vertical direction by pixel.

According to another aspect of the present invention, a method ofdisplaying a three-dimensional image in a three-dimensional imagedisplay device which has a two-dimensional image display screen having acolor filter in which each color is disposed on sub-pixels obtained bydividing one pixel in a vertical direction and same color is disposed oneach column of sub-pixels, and an optical plate having an exit pupil,the exit pupil being provided for making a1

viewing zone different for each pixel and having a longitudinal axisdisposed as to be inclined from a vertical direction of thetwo-dimensional image display screen at a degree (θ) (θ≠0, −45°<θ<45°),the viewing zone being a region in which parallax information displayedon the two-dimensional image display screen is observed, includesshifting the viewing zone in a horizontal direction of thetwo-dimensional image display screen by shifting the parallaxinformation disposed on each pixel of the two-dimensional image displayscreen in the vertical direction by pixel.

A computer program product according to still another aspect of thepresent invention causes a computer to perform the method according tothe present invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an entire structure of a three-dimensional image displaydevice according to a first embodiment of the present invention;

FIG. 2 shows a two-dimensional image display screen of thethree-dimensional image display device;

FIG. 3 shows an inclined line of an optical plate relative to a pixel ofthe two-dimensional image display screen of FIG. 2;

FIG. 4 is a block diagram showing a functional structure of a displayimage processing unit shown in FIG. 1;

FIG. 5 shows an arrangement of parallax information disposed by a deviceinformation holding unit shown in FIG. 4;

FIG. 6 is an enlarged view of one elemental image in the parallaxinformation shown in FIG. 5;

FIGS. 7A and 7B schematically show a relationship between a disposingposition of the elemental image and a viewing zone;

FIG. 8 shows shifting of the elemental image array in the horizontaldirection;

FIG. 9 shows a result of shifting of the elemental image array shown inFIG. 6 by one pixel in the vertical direction;

FIG. 10 shows a result of further shifting of the elemental image arrayshown in FIG. 9 by one pixel in the vertical direction;

FIG. 11 shows a result of shifting of the elemental image array by threepixels;

FIG. 12 shows a result of shifting of the elemental image array by fourpixels;

FIG. 13 is a flowchart showing a position displacement correctionprocess by the three-dimensional image display device according to thefirst embodiment;

FIG. 14 schematically shows a shift of the viewing zone according to amovement of the observer in y-direction;

FIG. 15 shows a flatbed-type three-dimensional image display device;

FIG. 16 is a diagram for explaining the position displacement correctionprocess in an integral imaging system;

FIG. 17 is a diagram for explaining the position displacement correctionprocess in a multi-lens type system;

FIG. 18 is a diagram of a hardware structure of the display imageprocessing unit of the three-dimensional image display device accordingto the first embodiment; and

FIG. 19 is a view showing a three-dimensional image display deviceaccording to a second embodiment.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, a three-dimensional image display device, athree-dimensional image display method, and a computer program productfor three-dimensional image display according to the present inventionwill be described in detail with reference to the drawings. The presentinvention is not limited to the embodiment.

FIG. 1 is a view showing an entire structure of a three-dimensionalimage display device 10 according to a first embodiment. Thethree-dimensional image display device 10 includes a display imageprocessing unit 100 that controls an arrangement of a parallaxinformation, a two-dimensional image display screen 200 that displaysthe parallax information, and an optical plate 300 that controls a rayfrom the two-dimensional image display screen 200. The two-dimensionalimage display screen 200 includes a liquid crystal layer 201 and a colorfilter layer 202.

The optical plate 300 in this embodiment is a lenticular sheet. Alongitudinal axis 302 of the optical plate 300 is inclined to left atarctan (¼) relative to a vertical direction of the two-dimensional imagedisplay screen 200. The two-dimensional image display screen 200displays parallax information according to the inclination thereof.

It is only necessary that the longitudinal axis 302 of the optical plate300 is inclined at a predetermined degree (θ≠0, −45°<θ<45°) relative tothe vertical direction of the two-dimensional image display screen 200,and a degree of the inclination is not limited to that of theembodiment.

The display image processing unit 100 adjusts a viewing zone in whichthe parallax information displayed on the two-dimensional image displayscreen 200 is observed, by changing a disposing position of the parallaxinformation displayed on the two-dimensional image display screen 200.

Meanwhile, in this embodiment, a depth direction, in which an observerside is positive, is z-direction. A horizontal direction of thetwo-dimensional image display screen 200, in which a right side of theobserver is positive, is x-direction. A vertical direction of thetwo-dimensional image display screen 200, in which an upper side ispositive, is y-direction.

FIG. 2 shows the two-dimensional image display screen 200, on whichsquare pixels are disposed in array. Each of the pixels includessub-pixels 231, 232, and 233, which are R (red), G (green), and B(blue), respectively.

Each of the sub-pixels 231, 232, and 233, which are R (red), G (green),and B (blue), respectively, is repeatedly disposed along the horizontaldirection in this order. In the vertical direction, every column iscomposed of the sub-pixels of same color. The R (red), G (green), and B(blue) sub-pixels are realized by a proper disposition of the colorfilter 202 on the display screen.

Herein, the reason for inclining the longitudinal axis of the opticalplate 300 at θ degree (≠0) relative to the sub-pixel column will bedescribed. When the three sub-pixels R, G, and B, which are disposedhorizontally, are treated as one pixel and the optical plate 300 isinclined, in order to improve horizontal definition, horizontaldefinition H and vertical definition V of a displayed three-dimensionalimage are represented by a following formulae (1):

H=Horiginal×3÷N÷a

V=Voriginal÷3×a   (1)

Herein, Horiginal represents the horizontal definition of thetwo-dimensional image display screen 200, whereas Voriginal representsthe vertical definition of the two-dimensional image display screen 200.Further, N represents a parallax number and “a” represents a ratio ofthe vertical definition assigned to the horizontal definition as aresult of the inclination of the optical plate 300.

In order to maintain the ratio of the horizontal definition Horiginal tothe vertical definition Voriginal of the two-dimensional image displayscreen 200, also in the three-dimensional image display device 10,Horiginal and Voriginal are required to satisfy a following formula (2):

Horiginal:Voriginal=(Horiginal×3÷N÷a):(Voriginal÷3×a)   (2)

A formula (3) is derived from the formula (2), and N is represented by aformula (4):

3/(N·a)=a/3   (3)

N=(3/a)²   (4)

Next, a principle of the assignment of the vertical definition to thehorizontal definition by the inclination of the optical plate will bedescribed. FIG. 3 shows an inclined line 310 of the optical plate 300relative to a pixel 230 of the two-dimensional image display screen 200.The inclined line 310 shown in FIG. 3 includes three inclined lineshaving different degrees θ. A region corresponding to the inclined line310 in FIG. 3 is observed by one eye through one of exit pupilssequentially disposed in a substantially vertical direction of theoptical plate 300, a focus of which conforms to the two-dimensionalimage display screen 200. When a position of the observer who observesthe three-dimensional image displayed on the three-dimensional imagedisplay device, that is, a viewing position, is moved, the regionindicated by the reference numeral 310 shifts in the horizontaldirection accordingly.

When the exit pupils of the optical plate 300 are sequentially disposedin the vertical direction in the same way as the above-described pixels,as in the conventional case, a pixel, a center of which is observedthrough one of the exit pupils of the optical plate 300 (the center ofwhich conforms to the region indicated by the reference numeral 310) iseither all of the pixels on one column or none, so that a switchingperiod of two states by the shift of the region indicated by thereference numeral 310 in accordance with the move of the observer,conforms to a horizontal width of the sub-pixel.

On the other hand, when the number of pixels, the center of whichconforms to the region indicated by the reference numeral 310, decreasesand the region indicated by the reference numeral 310 moves inaccordance with the move of the observer due to the inclination of theoptical plate 300, a period in which the pixel, the center of whichconforms to the region, appears becomes shorter than the horizontalwidth of the sub-pixel. Further, when the center of the pixel isselected, there is necessarily a non-display portion, which is aboundary portion of the horizontally adjacent sub-pixels in the regionindicated by the reference numeral 310.

In FIG. 3, an example in which the optical plate 300 is inclined at arate of four, five, and six sub-pixels in the vertical direction perthree sub-pixels in the horizontal direction is shown. when the opticalplate 300 is inclined at the rate of four sub-pixels, five sub-pixels,and six sub-pixels in the vertical direction per three sub-pixels in thehorizontal direction, a positional relationship between the regionindicated by the reference numeral 310 and the pixel is identical everythree sub-pixels, every four sub-pixels, and every other sub-pixels,respectively. That is, the number of the pixels having the same relativeposition relative to the region indicated by the reference numeral 310(i.e., the pixels, whose observed portion is identical with each other,when observed through one of the exit pupils sequentially disposed onthe substantially vertical direction) decreases to a quarter, a fifthpart, and a half, respectively. On the other hand, in the horizontaldirection, the pixels the center of which conforms to the regionindicated by the reference numeral 310 appears in a period of a quarterthe sub-pixel width, a fifth part of the sub-pixel width, and a half thesub-pixel width as compared with the period of the pixels in the opticalplate which is perpendicular to the pixels. In other words, thehorizontal definition increases four times, five times, and twice,respectively.

When the parallax information is divided by sub-pixel pitch, a form ofthe sub-pixel affects a degree of distribution of the parallaxinformation. A liquid crystal display, for example, used as thetwo-dimensional image display device, is designed such that three RGBsub-pixels form one square pixel. Further, in a design for displayingnumerous vertical straight lines such as characters, a color filter ofvertical stripe arrangement is frequently used. Therefore, the form ofthe sub-pixel here is set to have a ratio of vertical length:horizontallength=3:1, as shown in FIG. 3.

When three sub-pixels dispersed in different three columns instead ofthree adjacent sub-pixels in the same row in the horizontal direction,are treated as one pixel, in order to improve the horizontal definitionin the three-dimensional image display device, inclination θ of theoptical plate is defined by a formula (5):

θ=arctan(1/n)   (5)

In the formula (5), n is an optional integer. The period, in which thepixel the center of which conforms to the region indicated by thereference numeral 310 appears, becomes 1/n of the sub-pixel width.Thereby, the horizontal definition per sub-pixel improves by n times,and three RGB sub-pixels adjacent to each other in the horizontaldirection, the centers of which conform to the region indicated by thereference numeral 310 by the 1/n period (which do not conform in thevertical direction), form one pixel (triplet). Therefore, a ratio “a” ofthe vertical definition assigned to the horizontal definition is givenby a formula (6):

a=3/n   (6)

In other words, when the three-dimensional image is displayed, anobservable positions of the RGB sub-pixels of the triplet are subtlyshifted (the centers of the three RGP sub-pixels and the regionindicated by the reference numeral 310 do not conform one another at thesame moment). Actually, even in a state in which the region indicated bythe reference numeral 310 and the centers of the pixels do not conform,a part of the pixels is visually recognized through the exit pupil, sothat a region in which the substantially conformed RGB sub-pixels areseen at the same moment, exists. Therefore, in the case of FIG. 3,θ=arctan (¼), arctan (⅕), and arctan (⅙), and the ratio “a” of thevertical definition assigned to the horizontal definition becomes a=¾, ⅗and ½, respectively.

Therefore, by satisfying the relationship between n and N so as tosatisfy the above-described formula (4), as well as making the opticalplate incline according to the formula (5), deterioration ratios of thedefinition in the horizontal and vertical directions can be conformed toeach other. That is, N and n are designed so as to satisfy a followingformula (7):

N=n²   (7)

FIG. 4 is a block diagram of the functional structure of the displayimage processing unit 100. The display image processing unit 100includes a parallax information preparing unit 101, a parallaxinformation holding unit 102, a device information holding unit 104, aparallax information disposing unit 110, a viewing position displacementdetecting unit 120, an adjustment information holding unit 122, anadjustment information obtaining unit 124, a shift amount determiningunit 130, a shift direction determining unit 132, an elemental imagearray shifting unit 134, and a surplus portion processing unit 140.

The parallax information preparing unit 101 prepares parallaxinformation. Specifically, the parallax information preparing unit 101prepares the parallax information, a size of which is larger than ascreen size of the two-dimensional image display screen 200. Theparallax information holding unit 102 holds the parallax informationprepared by the parallax information preparing unit 101. The deviceinformation holding unit 104 holds device information. As used herein,the device information is intended to mean information about thetwo-dimensional image display screen 200 and the optical plate 300, andspecifically, is information about the screen size, a color alignment ofthe sub-pixels, and the like.

The parallax information disposing unit 110 disposes the parallaxinformation held by the parallax information holding unit 102 on each ofthe pixels on the two-dimensional image display screen 200. At thismoment, the parallax information disposing unit 110 determines thedisposing position of each of the parallax information, based on thedevice information held by the device information holding unit 104.

FIG. 5 shows parallax information 400 disposed according to the deviceinformation held by the device information holding unit 104. Theparallax information shown in FIG. 4 includes sixteen parallaxinformations in total from a first parallax information to a sixteenthparallax information. Numerals represented in each of the pixelsindicate the number of the parallax information.

As shown in FIG. 4, the parallax informations having a same referencenumeral are disposed on positions corresponding to an inclination degree(θ) of the longitudinal axis 302 of the optical plate 300. For example,the first parallax informations are disposed along an inclined line 312inclined at the inclination degree θ. Further, the fourth parallaxinformations are disposed along an inclined line 314 inclined at theinclination degree θ.

FIG. 6 is an enlarged view showing one elemental image 410 of theparallax information 400 shown in FIG. 5. The elemental image 410 is anassembly of plural sub-pixels for displaying the parallax informationcorresponding to one pixel for displaying the three-dimensional image.The elemental image 410 of the first embodiment includes fifteen pixelsalong the horizontal direction and four pixels along the verticaldirection. Further, a boundary position along the vertical direction isshifted to right by one sub-pixel as the boundary goes downwards in thevertical direction, and the elemental image 410 is a substantiallyparallelogram-shape.

The viewing position displacement detecting unit 120 detectsdisplacement between the viewing position, which is a position of theobserver supposed in the three-dimensional image display device 10 inadvance and an actual position of the observer, that is, viewingposition displacement. Further the viewing position displacementdetecting unit 120 detects a degree of the viewing positiondisplacement.

Specifically, the viewing position displacement detecting unit 120detects an x-coordinate of a position of the head of the observer byimage recognition, and performs tracking. Further, when thus obtainedx-coordinate does not conform to the x-coordinate of the assumed viewingposition, the viewing position displacement detecting unit 120 detectsthis as the position displacement. Further, the viewing positiondisplacement detecting unit 120 detects the displacement as a viewingposition displacement amount in the x-direction. Further, the viewingposition displacement detecting unit 120 also detects the viewingposition displacement and the viewing position displacement amount inthe y-direction.

Meanwhile, when the three-dimensional image display device 10 is setvertically, the viewing position displacement in the y-direction doesnot matter. Thus, in this case, only the viewing position displacementand the viewing position displacement amount in the x-direction may bedetected. Further, when the three-dimensional image display device 10 isa flatbed display, only the viewing position displacement and theviewing position displacement amount in the y-direction may be detected.

The adjustment information holding unit 122 holds adjustmentinformation. The adjustment information is, for example, an opticalplate position displacement amount indicating a degree of thedisplacement of a set degree of the optical plate 300 during the use ofthe three-dimensional image display device 10, and of an attachingposition, generated when the optical plate 300 is attached to thetwo-dimensional image display screen 200. The adjustment informationobtaining unit 124 obtains the adjustment information input by a user,and makes the adjustment information holding unit 122 hold the same.

The three-dimensional display device 10 according to the firstembodiment can shift the viewing zone in the horizontal direction of thetwo-dimensional image display screen 200 according to the viewingposition displacement and the adjustment information, by adjusting thedisposing position of the parallax information. Hereinafter, thefunction and structure for this will be described.

The shift amount determining unit 130 determines an amount of shiftingthe elemental image array, based on the viewing position displacementamount detected by the viewing position displacement detecting unit 120,and the adjustment information held by the adjustment informationholding unit 122. Herein, a process of the shift amount determining unit130 is described in detail, with reference to FIGS. 7A and 7B. FIGS. 7Aand 7B illustrate a relationship between the disposing position of theelemental image array and the viewing zone.

For example, the region in which the elemental image arrays disposed onthe disposing positions 210, 212, and 214 are observed is a viewing zone512. Further, the region in which the elemental image arrays disposed onthe disposing positions 220, 222, and 224, which moved in thez-direction from the disposing positions 210, 212, and 214,respectively, are observed is a viewing zone 514.

That is, when the position of the head of the observer moves from aposition 510 to a position 520, the viewing zone can be turned to adirection of the observer while holding a vision of thethree-dimensional image, by shifting the disposing position of theelemental image array in the x-direction according to a move amount ofthe observer, while maintaining disposition of each parallax informationin the elemental image arrays.

More specifically, when a gap between the two-dimensional image displayscreen 200 and the optical plate 300 is represented by “g” and a visualdistance of the observer is represented by “L,” a shift amount (xe) ofthe elemental image array for making the viewing zone follow theobserver who moved by +x1 in the x-direction is represented by a formula(8):

xe=−(g/L)×x1   (8)

In other words, it is only necessary that the elemental image array isshifted by the shift amount (xe) in the x-direction. The shift amountdetermining unit 130 determines the shift amount (xe) from the formula(8) by using the position displacement amount detected by the viewingposition displacement detecting unit 120, that is, an amount x1.

The shift direction determining unit 132 determines a direction to whichthe elemental image array is shifted, based on the shift amountdetermined by the shift amount determining unit 130. Herein, a processof the shift direction determining unit 132 is described in detail, withreference to FIG. 8. FIG. 8 shows shifting of the elemental image arrayin the horizontal direction. Since the image information can be treatedonly by pixel (triplet), which is a minimum unit of the shift, whenshifting the elemental image array in the horizontal direction.

For example, suppose that the elemental image is mapped on thetwo-dimensional image display screen 200, as shown in FIG. 5. Further,sub-pixel pitch of the two-dimensional image display screen 200 is setto xsp. The displacement degree (θ) of the optical plate 300 relative tothe vertical direction of an edge line of a lens is defined by a formula(9):

θ=atan(1/n)   (9)

where n is an optional integer.

Under the above-described condition, an interval xp in which theparallax information is presented with the visual distance (L) isrepresented by a formula (10):

xp=xsp×3/n×L/g   (10)

The minimum value of the shift amount xs of a visual region, when theelemental image is shifted by pixel is represented by a formula (11):

xs=xsp×3×L/g=xp×n   (11)

Since n is an optional integer, it is found from the formula (11) thatthe elemental image array can be shifted only by unit larger than theinterval xp unit in which the parallax information is presented.

For example, when a WUXGA panel of 15.4 inches is used, the sub-pixelpitch xsp is set to 57.5 μm, g=1.334 mm, and L=400 mm, and mapping ofthe elemental image 410 is as shown in FIG. 6, the interval xp in whichthe parallax information is presented is 12.93 mm, from the formula(10).

On the other hand, the shift amount of the visual region is 51.72 mm atthe minimum, which is larger than the interval xp, when the elementalimage 410 is shifted in the horizontal direction by pixel pitch,according to the formula (11). In other words, when the observer movesin the x-direction, the visual region follows the observer after movingby approximately 5 cm in the horizontal direction, so that it isrecognized as flipping.

By shifting the elemental image array by pixel in the vertical directionof the two-dimensional image display screen 200, a similar shift of thevisual region as the shift by one sub-pixel in the horizontal directionbecomes possible. Hereinafter, the shift in the vertical direction willbe described with reference to FIGS. 9 to 12.

FIG. 9 shows a result of shifting of the elemental image array shown inFIG. 6 by one pixel in the vertical direction. In FIG. 6, the firstparallax informations are disposed on the inclined line 312. On theother hand, after the array is shifted by one pixel in the verticaldirection, as shown in FIG. 9, the second parallax informations aredisposed on the inclined line 312. In brief, by shifting the elementalimage array by one pixel in the vertical direction, a dispositionsimilar to that in which the elemental image array is shifted by oneparallax information in the horizontal direction is achieved.

FIG. 10 shows a result of further shifting of the elemental image arrayshown in FIG. 9 by one pixel in the vertical direction. In other words,FIG. 10 shows a result of shifting of the elemental image array shown inFIG. 6 by two pixels. In FIG. 10, the third parallax informations aredisposed on the inclined line 312.

FIG. 11 shows a result of shifting of the elemental image array by threepixels. FIG. 12 shows a result of shifting of the elemental image arrayby four pixels. As is found by comparing FIGS. 11 and 8, the parallaxinformations disposed on the inclined line 312 after the elemental imagearray is shifted by four pixels in the vertical direction, and theparallax informations disposed on the inclined line 312 after the arrayis shifted by one pixel in the horizontal direction are both the fifthparallax informations.

In this manner, the shift by four pixels in the vertical directioncorresponds to the shift by one pixel in the horizontal direction. Inother words, the shift by a quarter pixel in the horizontal direction isrealized by the shift by one pixel in the vertical direction.

For example, as described above, when the elemental image array isshifted by one pixel in the horizontal direction, the visual region isshifted by 51.72 mm. However, when the array is shifted by one pixel inthe vertical direction, the viewing zone can be shifted by pitch of51.72 mm/4 mm. The shift amount of the visual region when the elementalimage array is shifted by one pixel in the vertical direction equals tothe interval (xp) represented by the formula (10).

Since the number of the pixels of the two-dimensional image displayscreen 200 is limited, a value of the interval (xp) is finite. The shiftof the visual region can be made identical to the interval in which theparallax information is presented (xp=xs) under this condition. In otherwords, the visual region can be made to follow perfectly smoothly in thesystem.

As described above, the shift of the viewing zone in the horizontaldirection, in which the minimum unit of which is smaller than that inthe shift in the vertical direction, is realized with the vertical shiftof the elemental image array. Then, the shift direction determining unit132 determines whether the elemental image array is shifted in thehorizontal direction or in the vertical direction, according to theshift amount determined by the shift amount determining unit 130.

When the longitudinal axis 302 is inclined so as to form a downwardslope as in the optical plate 300 according to this embodiment, in otherwords, when the inclination degree θ of the longitudinal axis 302satisfies −45°<θ<0°, the elemental image array may be shifted downwardfrom top to bottom of the two-dimensional image display screen 200, inorder to shift the elemental image array from a right side to a leftside of the two-dimensional image display screen 200 seen from anobserver side. Further, the elemental image array may be upward shiftedfrom below the two-dimensional image display screen 200, in order toshift the elemental image array from the left side to the right side.

Further as another example, when the longitudinal axis 302 of theoptical plate 300 slopes down to left, in other words, when theinclination degree θ of the longitudinal axis 302 satisfies 0°<θ<45°,the elemental image array may be shifted upward from the bottom to thetop, in order to shift the elemental image array from right side to leftside. In order to shift the elemental image array from the left side tothe right side, the elemental image array may be shifted from the top tothe bottom.

Meanwhile, along with the shift of the elemental image array, thethree-dimensional image itself is shifted upwards or downwards. However,since the shift amount is product of pixel pitch and shift amount, shiftof the three-dimensional image in the vertical direction is as small as517.5 μm (=xsp×3×3), for example, even when the elemental image array isshifted by three pixels as shown in FIG. 11, and hence, the verticalshift of the three-dimensional image does not become problematic.

When the shift amount is equal to or larger than this, the shift in thevertical direction may be increased. Alternatively, the shift in thehorizontal direction may be combined. The shift by one pixel in thehorizontal direction equals to the shift by four pixels in the verticaldirection. Hence, when the shift amount is equal to or larger than onepixel in the horizontal direction, the shift in the horizontal directionis combined. Thereby, it becomes possible to narrow a surplus portiongenerated by the shift of the elemental image array. Herein, the surplusportion is intended to mean the pixel region to which the parallaxinformation is not assigned as a result of the shift of the elementalimage array. For example, in FIG. 12, a region 420 is the surplusportion.

Further, by combining the shifts in the horizontal direction and in thevertical direction in this manner, it becomes possible to minimize thedisplacement of the display position of the three-dimensional imagecaused by the shift of the elemental image array.

FIG. 4 is described again. The elemental image array shifting unit 134shifts the elemental image array by the shift amount determined by theshift amount determining unit 130 in the shift direction determined bythe shift direction determining unit 132. The surplus portion processingunit 140 assigns an appropriate image to the surplus portion generatedafter shifting by the elemental image array shifting unit 134.Specifically, the elemental image array disposed before the shifting isassigned.

Alternatively, an image to be assigned to the surplus portion may beheld in advance and assigned. A black image, for example, may be used assuch an image.

As described above, the parallax information is the information, thesize of which is larger than the screen size of the two-dimensionalimage display screen 200. In order to minimize the surplus portiongenerated at the shifting of the elemental image array, the information,the size of which is larger than the screen size of the two-dimensionalimage display screen 200, is generated. In this manner, since the sizeof the parallax information is larger than the screen size of thetwo-dimensional image display screen 200, the surplus portion may beminimized, and the three-dimensional image can be displayed withaccuracy even when the elemental image array is shifted.

FIG. 13 is a flowchart of a position displacement correction process bythe three-dimensional image display device 10 according to the firstembodiment. The parallax information disposing unit 110 determines adisposing position of the parallax information based on the deviceinformation held by the device information holding unit 104 (step S100).Next, the parallax information disposing unit 110 disposes the parallaxinformation held by the parallax information holding unit 102 on thedetermined disposing position (step S102).

Next, the shift amount determining unit 130 determines the shift amountbased on the viewing position displacement amount detected by theviewing position displacement detecting unit 120 and the adjustmentvalue held by the adjustment information holding unit 122 (step S104).Then, the shift direction determining unit 132 determines the shiftdirection based on the shift amount determined by the device informationholding unit 104 (step S106). Further, the elemental image arrayshifting unit 134 shifts the elemental image array (step S108). Further,the parallax information disposing unit 110 assigns an appropriate imageto the surplus portion generated by the shift (step S110). Herewith, theposition displacement correction process ends.

The above-described position displacement correction process may beperformed at the fabrication of the three-dimensional image displaydevice 10, or after the shipment of the same by instruction of the user.

First, a correction process of the viewing position displacement isdescribed. When the observer moves to the y-direction, it is possible tomake the viewing zone move to the position where the observer moves, bymaking the viewing zone shift in the x-direction.

FIG. 14 illustrates the shift of the viewing zone in accordance with themove of the observer in the y-direction. As shown in FIG. 14, when theobserver observes the three-dimensional image in an observing direction(1), that is, the z-direction, which is a normal line direction of thetwo-dimensional image display screen 200, the pixels on a viewingposition (1) are observed. If the observing direction moves todirections (2) and (3), the viewing positions are accordingly shifted topositions (2) and (3), respectively.

Thus, when the y coordinate of the observer shifts, the position of theparallax information relative to the exit pupil, or the position of theexit pupil relative to the parallax information relatively moves in thex-direction. In other words, when the observer moves to the y-direction,the viewing zone is shifted to the x-direction.

The shift of the viewing zone along with the move of the observer in they-direction is especially noticeable when a horizontal parallax typethree-dimensional image display device is set such that a displaysurface thereof is horizontal, i.e., when the device is used as aflatbed display device.

FIG. 15 shows a three-dimensional image display device 10 of a flatbedtype. As shown in the drawing, in the case of the flatbed-typethree-dimensional image display device 10, the observer looks down thescreen of the three-dimensional image display device 10 from above.Hence, the y coordinate of the viewing position is affected by theposition and the sitting height of the observer. Therefore, the viewingposition easily varies as compared to that of the vertically set displaydevice.

The three-dimensional image display device 10 according to the firstembodiment can deal with such variation in the viewing position withhigh accuracy.

This will be described more specifically. When the viewing positionmoves in the y-direction (displacement amount: y1), the shift amount xsof the viewing zone in the horizontal direction is represented by aformula (12):

xs=b×L/g   (12)

Herein, b is a value of a horizontal displacement width in a singlepixel row of the two-dimensional image display device observed through asingle exit pupil when the viewing position moves in the y-direction,and is represented by a formula (13):

b=a×tan θ  (13)

Further, “a” represents an interval width between a slit position andthe viewing position, and is represented by a formula (14):

a=g/tan φ  (14)

Herein, tan φ is defined by a following formula (15):

tan φ=L/y1   (15)

Thus, the formula (12) is transformed as a formula (16):

xs=b×L/g=(g/tan φ)×tan φ×L/g=tan θ×L/tan φ  (16)

Therefore, if the above-described horizontal parallax typethree-dimensional image display device is horizontally set as a flatbeddisplay and observed with angle of depression of 45°, the viewing zoneis shifted no less than 100 mm in the horizontal direction as comparedto a case where the device is observed from front (with angle ofdepression of 90°).

If the parallax number is set to N (N=16, in the first embodiment), theviewing zone (VW) is represented by a formula (17):

VW=N×3/4×xsp×L/g   (17)

Therefore, under the condition of the first embodiment, VW=206.89 mm.Further, the interval (xp) in which the parallax information ispresented is 12.93 mm as described above.

So, if the viewing zone is shifted by 100 mm, this is equivalent thatthe viewing zone is shifted approximately halfway. In other words, ifthe image, which is set on the assumption that the angle of depressionis 45°, is observed from right above the display by the observer wholeans over the display, the position of the head of the observer is onthe edge of the visual region.

Further, if the y coordinate of the observer (L=400 mm) moves as shortas 4 cm, the viewing zone is shifted by 10 mm, i.e., approximately oneparallax in the horizontal direction. This indicates that positioning ofthe lens while assuming the angle of depression is difficult.

The three-dimensional image display device 10 according to the firstembodiment can solve the above-described problem. As already described,the three-dimensional image display device 10 according to the firstembodiment can shift the viewing zone with a minimum unit of 12.93 mm.

Therefore, if the observer moves from the position with the angle ofdepression of 45° to the position with the angle of depression of 90°,the viewing zone may be shifted by one to eight pixels in the verticaldirection, in accordance with the move. Further, when the region isshifted by four pixels or more, the shift in the horizontal directioncan be combined.

The positioning of the two-dimensional image display screen 200 and theoptical plate 300 is performed in the fabricating process. When theoptical plate 300 is attached to the two-dimensional image displayscreen 200, displacement of an attaching position, that is, thedisplacement of the optical plate becomes problematic. The alignment ofthe two-dimensional image display screen 200 and the optical plate 300affects the viewing zone of the three-dimensional image display device10, and hence sufficient accuracy is required.

In the horizontal parallax system, there is a case where the parallaxinformation is disposed by sub-pixel pitch of a FPD, in order toincrease the horizontal parallax number. In this case, the parallaxinformation is shifted by one with a shift by the sub-pixel width(approximately 50 μm). If the exit pupil is inclined from the verticaldirection, it is required to assume the angle of depression, that is,the y coordinate, when setting the viewing zone, which makes thepositioning even more difficult.

The three-dimensional image display device 10 can correct the viewingzone according to such displacement of the optical plate 300.Specifically, if the user inputs such an optical plate displacementamount, the adjustment information obtaining unit 124 obtains theoptical plate displacement amount as the adjustment information, andholds the same. Further, the three-dimensional image display device 10shifts the elemental image array according to the optical platedisplacement amount, and sets a disposing position after the shift as adefault value. Thereby, the displacement of the optical plate 300 can becompensated. In brief, yield ratio can be improved by recovery.

Further, in the fabricating process, the optical plate 300 is attachedby observing from a normal line direction of the two-dimensional imagedisplay screen 200, and after that, the angle of depression (φ) ismeasured. Further by an input of the angle of depression by the user,the adjustment information holding unit 122 obtains the angle ofdepression input by the user through the adjustment informationobtaining unit 124, and holds the same. The elemental image 410 may beshifted according to the held angle of depression, and the disposingposition after the shift may be set as the default value. Thereby, adevice can be manufactured irrespective of type of usage.

Further, there is a case where the user wants to use thethree-dimensional image display device 10 in both vertical andhorizontal setting. In this case, the three-dimensional image displaydevice 10 can correct the visual region according to the displacementamount generated from the inclination degree of the three-dimensionalimage display device 10 itself. Specifically, the inclination degree ofthe three-dimensional image display device 10 is obtained by the inputof the user. Further, by shifting the elemental image 410 according tothe setting degree, an appropriate three-dimensional image can bedisplayed for each type of usage.

Further, there is a case where the optical plate displacement isgenerated according to the change over time after fabrication. Forexample, such displacement could be generated by an environment or aphysical shock after the shipment. In this case, the three-dimensionalimage display device 10 can adjust the disposing position according tothe optical plate displacement amount.

The three-dimensional image display device 10 holds an image foradjustment, which is used at the correction of such optical platedisplacement, to perform a displacement correction process using thisimage. Hereinbelow, a case with an integral imaging system will bedescribed. FIG. 16 illustrates the displacement correction process inthe integral imaging system.

When horizontal pitch of the exit pupil is set to integral multiple ofthe sub-pixel pitch, rays which exit from the pixels having the sameparallax number (camera number) are in a substantially parallelrelationship, as shown in FIG. 16.

For example, suppose that only the sub-pixels, on which the firstparallax information is disposed in FIG. 5, are illuminated and othersare not illuminated. When the display is observed in this state from aviewing position 530 away from the display by a distance L, with oneeye, emission lines extending in the vertical direction with constantintervals, are observed.

If the interval is set to xt, a horizontal interval between the pixelson which the first parallax information is disposed is set to pi, and aninterval between the pixels on which the first parallax informationsimultaneously seen by one eye is disposed is set to pii, formulae (18)to (20) are obtained:

pi=xsp×N×3/n   (18)

pii=pi×(xt/pi+1)   (19)

pii=(L+g)/L×xt   (20)

By assigning the previously described formulae into the formulae (18) to(20), a formula (21) can be obtained:

xt=pii−pi=3×xsp×N/n/((L+g)/L−1)   (21)

When the previously described conditions are assigned into the formula(21), xt=206.9 mm. That is, the emission lines are visually recognizedas vertical stripes with intervals of approximately slightly above 20cm. The display positions of the emission lines are uniquely determinedaccording to the relation between the illuminated parallax informationand the position of the optical plate 300. Therefore, by making theimage for adjustment and the display position (x coordinate) of theemission line correspond to each other, it becomes possible to confirmthe optical plate displacement by visually recognizing the positiondisplacement and the inclination of the emission lines.

For example, if the optical plate position is shifted by one sub-pixelin the x-direction, the position of the emission line is shifted by xsrepresented by a formula (22):

xs=xsp×L/g   (22)

When the elemental image 410 is disposed as shown in FIG. 5, when theemission line is shifted by xf in the x-direction, the elemental imagearray may be shifted downward by (xf/xs) rows.

When mounting the same, for example, a key to sequentially shift theelemental image array upward or downward (horizontally), in a conditionin which the user is on the viewing position, is provided, and makes theuser adjust by pressing the key until the emission lines have desiredintervals.

An ideal display position of the emission lines may be presented by adocument or the like, or presented in some way outside the displayregion for the three-dimensional image (for example, a casing) of thethree-dimensional image display device.

Furthermore, the elemental image array including an image forpositioning can be prepared by dividing the elemental image array in twoportions in the vertical direction. An image for adjustment (A) isdisplayed on one of the two portions. Further, a guide image (B)indicating the x coordinate on which the emission lines should bedisplayed is displayed on the other portion. The guide image may be in acondition in which all the elemental images corresponding to the exitpupils relevant to the x coordinate on which the emission lines are tobe indicated, are illuminated.

When all the corresponding elemental images are illuminated, theelemental images in a certain range (=viewing zone) are sequentiallyseen illuminated. Therefore, even if the position of the exit pupil isshifted a little, if this is not shifted halfway the elemental imagewidth or more, these elemental images are always seen illuminated, whenthis is observed by one eye in the viewing zone. In such a condition, anentire image (A+B) including the elemental image array is shifted up anddown, and to the right and the left, thereby making the x coordinate ofthe lens which illuminates in a (B) range and the x coordinate of thelens which illuminates in a (A) range substantially conform to eachother.

Next, a case of multi lens system is described. FIG. 17 illustrates aposition displacement correction process in a multi lens system.Horizontal pitch of the exit pupil of the multi lens system is set toL/(L+g), which is an integral multiple of the sub-pixel pitch.Consequently, as shown in FIG. 17, rays exit from the pixels on whichthe identical parallax information is disposed are focused on a position540 with a visual distance L.

For example, suppose that only the sub-pixels on which the firstparallax information is disposed, which are disposed as shown in FIG. 5are illuminated and others are not illuminated. In this case, if theimage is observed by one eye from the distance L, the image is observedsuch that the entire image is illuminated. However, if this is observedfrom a point off from a designed visual distance L, a range ofilluminated pixels is narrowed (only the pixels directly in front of theobserver are seen illuminated). In other words, when the image isobserved from a position slightly off from the visual distance L, theinclination of the optical plate 300 can be confirmed. For example, ifthe optical plate 300 is attached to the two-dimensional image displayscreen 200 as to be inclined relative to the two-dimensional imagedisplay screen 200, the illuminated region observed from a position offfrom the visual distance L is also inclined. Further, when an attachingposition of the optical plate 300 is shifted in the x-direction, theentire image is seen not illuminated.

Therefore, when the user is made to operate the key to shift theelemental image array in up-and-down (horizontal) direction toilluminate the entire image, displacement of the lens position may becompensated by up-and-down (vertical) shift of the elemental imagearray.

FIG. 18 is a block diagram of a hardware structure of the display imageprocessing unit 100. The display image processing unit 100 is providedwith a read only memory (ROM) 52 that stores the displacement correctionprogram for executing the displacement correction process in thethree-dimensional image display device 10, or the like, a centralprocessing unit (CPU) 51 that controls each unit of thethree-dimensional image display device 10 according to the program inthe ROM 52, a random access memory (RAM) 53 that stores various datarequired for controlling the three-dimensional image display device 10,a communication interface (I/F) 57 that communicates by connecting to anetwork, and a bus 62 that connects respective units with each other, asthe hardware structure.

The above-described displacement correction program in the display imageprocessing unit 100 may be stored in a computer-readable recordingmedium, such as a compact disc read only memory (CD-ROM), a Floppy(Registered trademark) Disk (FD), a digital versatile disk (DVD) or thelike, as an installable or an executable file, and provided.

In this case, the displacement correction program is read out from theabove-described recording medium and executed by the display imageprocessing unit 100 to be loaded on a main memory, and each of the unitsexplained in the above-described software structure is generated on themain memory.

Further, the displacement correction program of the first embodiment maybe configured to be stored on the computer connected to a network suchas the Internet or the like, and to be provided by being downloadedthrough the network.

While the present invention has been explained in connection with theembodiment, various modifications and improvements can be made to theabove-described embodiment.

FIG. 19 is a view showing a three-dimensional image display device 20according to a second embodiment. A three-dimensional image displaydevice 20 according to the second embodiment is a portable type. Thethree-dimensional image display device 10 according to the secondembodiment includes an inclination detecting unit 210.

As a usage pattern of the portable type three-dimensional image displaydevice 20, it is envisaged that the user holds the same in his/her handand observes the three-dimensional image displayed on thethree-dimensional image display device 20. In this case, the viewingzone is shifted according to a relative angle between thethree-dimensional image display device 20 and the viewing position.

When the user holds the three-dimensional image display device 20 inhis/her hand, the relative angle may continually vary. Then, in additionto detection of the viewing position of the user, an inclination of thethree-dimensional image display device 20 itself is detected. Further,according to the result of detection, a relative position displacementand a degree of the displacement of the observer relative to thetwo-dimensional image display screen 200 is detected.

Other structure and process of the three-dimensional image displaydevice 20 according to the second embodiment are similar to those of thethree-dimensional image display device 10 according to the firstembodiment.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A three-dimensional image display device comprising: atwo-dimensional image display screen having color filters in which eachcolor is disposed on sub-pixels obtained by dividing one pixel in avertical direction and same color is disposed on each column ofsub-pixels; an optical plate having an exit pupil, the exit pupil beingprovided for making a viewing zone different for each pixel and having alongitudinal axis disposed as to be inclined from a vertical directionof the two-dimensional image display screen at a degree (θ) (θ≠0,−45°<θ<45°), the viewing zone being a region in which parallaxinformation displayed on the two-dimensional image display screen isobserved; and a viewing zone adjusting unit that adjusts the viewingzone by shifting the viewing zone in a horizontal direction of thetwo-dimensional image display screen by shifting the parallaxinformation disposed on each pixel of the two-dimensional image displayscreen in the vertical direction by pixel.
 2. The three-dimensionalimage display device according to claim 1, wherein the viewing zoneadjusting unit shifts the viewing zone in the horizontal direction byfurther shifting the parallax information in the horizontal direction bypixel.
 3. The three-dimensional image display device according to claim2, further comprising: a shift direction determining unit thatdetermines whether to shift the parallax information in the verticaldirection or the horizontal direction, according to a shift amount ofthe viewing zone to be shifted by the viewing zone adjusting unit,wherein the viewing zone adjusting unit shifts the parallax informationin the shift direction by the number of pixels according to the shiftamount.
 4. The three-dimensional image display device according to claim1, wherein the longitudinal axis of the exit pupil of the optical plateis disposed in a direction inclined from the vertical direction of thetwo-dimensional image display screen at a degree (−45°<θ<0°), and theviewing zone adjusting unit shifts the parallax information from top tobottom in the vertical direction by pixel, when shifting the viewingzone from a right side to a left side when viewed from an observer sidein the horizontal direction of the two-dimensional image display screen.5. The three-dimensional image display device according to claim 1,wherein the optical plate is disposed in a direction inclined from thevertical direction of the two-dimensional image display screen at adegree (−45°<θ<0°), and the viewing zone adjusting unit shifts theparallax information from bottom to top in the vertical direction bypixel, when shifting the viewing zone from a left side to a right sidewhen viewed from an observer side in the horizontal direction of thetwo-dimensional image display screen.
 6. The three-dimensional imagedisplay device according to claim 1, wherein the optical plate isdisposed in a direction inclined from the vertical direction of thetwo-dimensional image display screen by a degree (0°<θ<40°), and theviewing zone adjusting unit shifts the parallax information from bottomto top in the vertical direction by pixel, when shifting the viewingzone from a right side to a left side when viewed from an observer sidein the horizontal direction of the two-dimensional image display screen.7. The three-dimensional image display device according to claim 1,wherein the optical plate is disposed in a direction inclined from thevertical direction of the two-dimensional image. display screen at adegree (0°<θ<45°), and the viewing zone adjusting unit shifts theparallax information from top to bottom in the vertical direction bypixel, when shifting the viewing zone from a left side to a right sidewhen viewed from an observer side in the horizontal direction of thetwo-dimensional image display screen.
 8. The three-dimensional imagedisplay device according to claim 1, further comprising: an viewingposition displacement detecting unit that detects an viewing positiondisplacement amount which is a displacement amount between an viewingposition on which a three-dimensional image displayed on thethree-dimensional image display device should be observed and an actualposition of an observer; and an viewing zone shift amount determiningunit that determines a shift amount of the viewing zone based on theviewing position displacement amount, wherein the viewing zone adjustingunit shifts the viewing zone by the shift amount.
 9. Thethree-dimensional image display device according to claim 8, furthercomprising: the viewing position holding unit that holds the viewingposition, wherein the viewing position displacement detecting unitrecognizes a position of the observer by image recognition, and detectsa difference value between the recognized position of the observer andthe viewing position held by the viewing position holding unit as theviewing position displacement amount.
 10. The three-dimensional imagedisplay device according to claim 8, wherein the viewing positiondisplacement detecting unit detects the viewing position displacementamount in the horizontal direction of the two-dimensional image displayscreen, and the viewing zone shift amount determining unit determinesthe shift amount of the viewing zone based on the viewing positiondisplacement amount in the horizontal direction.
 11. Thethree-dimensional image displaying device according to claim 8, whereinthe viewing position displacement detecting unit detects the viewingposition displacement amount in the vertical direction of thetwo-dimensional image display screen, and the viewing zone shift amountdetermining unit determines the shift amount of the viewing zone basedon the viewing position displacement amount in the vertical direction.12. The three-dimensional image display device according to claim 8,further comprising: an inclination detecting unit that detects aninclination of the two-dimensional image display screen; and a viewingzone shift amount determining unit that determines the shift amount ofthe viewing zone based on the inclination, wherein the viewing zoneadjusting unit shifts the viewing zone by the shift amount.
 13. Thethree-dimensional image display device according to claim 1, furthercomprising: an optical plate position displacement amount obtaining unitthat obtains from outside an optical plate position displacement amountwhich is a displacement amount between the two-dimensional image displayscreen and the optical plate; and a viewing zone shift amountdetermining unit that determines the shift amount of the viewing zonebased on the optical plate position displacement amount, wherein theviewing zone adjusting unit shifts the viewing zone by the viewing zoneshift amount.
 14. The three-dimensional image display device accordingto claim 1, further comprising a surplus portion processing unit thatdisposes the parallax information on a pixel, which is located on thetwo-dimensional display screen and on which the parallax information isnot disposed after the shift of the parallax information.
 15. Thethree-dimensional image display device according to claim 1, furthercomprising a surplus portion processing unit that disposes a black imageon a pixel, which is located on the two-dimensional display screen andon which the parallax information is not disposed after the shift of theparallax information.
 16. The three-dimensional image display deviceaccording to claim 1, further comprising: a parallax information holdingunit that holds the parallax information, a size of which is larger thana size of the two-dimensional image display screen, wherein thetwo-dimensional image display screen displays the parallax informationheld by the parallax information holding unit.
 17. The three-dimensionalimage display device according to claim 16, further comprising aparallax information preparing unit that prepares the parallaxinformation, the size of which is larger than the size of thetwo-dimensional image display screen, wherein the parallax informationholding unit holds the parallax information prepared by the parallaxinformation preparing unit.
 18. A method of displaying athree-dimensional image comprising: in a three-dimensional image displaydevice including a two-dimensional image display screen having colorfilters in which each color is disposed on sub-pixels obtained bydividing one pixel in a vertical direction and same color is disposed oneach column of sub-pixels, and an optical plate having an exit pupil,the exit pupil being provided for making a viewing zone different foreach pixel and having a longitudinal axis disposed as to be inclinedfrom a vertical direction of the two-dimensional image display screen ata degree (θ) (θ≠0, −45°<θ<45°), the viewing zone being a region in whichparallax information displayed on the two-dimensional image displayscreen is observed, shifting the viewing zone in a horizontal directionof the two-dimensional image display screen by shifting the parallaxinformation disposed on each pixel of the two-dimensional image displayscreen in the vertical direction by pixel.
 19. A computer programproduct having a computer readable medium including programmedinstructions, wherein the instructions, when executed by a computer,cause the computer to perform: in a three-dimensional image displaydevice including a two-dimensional image display screen having colorfilters in which each color is disposed on sub-pixels obtained bydividing one pixel in a vertical direction and same color is disposed oneach column of sub-pixels, and an optical plate having an exit pupil,the exit pupil being provided for making a viewing zone different foreach pixel and having a longitudinal axis disposed as to be inclinedfrom a vertical direction of the two-dimensional image display screen ata degree (θ) (θ≠0, −45°<θ<45°), the viewing zone being a region in whichparallax information displayed on the two-dimensional image displayscreen is observed, shifting the viewing zone in a horizontal directionof the two-dimensional image display screen by shifting the parallaxinformation disposed on each pixel of the two-dimensional image displayscreen in the vertical direction by pixel.